John S Ma

51597110, Oct 27, 1992

Jan 24, 1990

7/469137

John Y. Ma - Milpitas CA
Chung W. Cheong - Kowloon, HK

Astec International Limited - Kowloon

H04B 110

455307

A TVRO receiver for receiving frequency-modulated video signals comprises a tuner including a super-heterodyne circuit having a voltage-controlled oscillator (VCO), means for supplying a cotnrolling input voltage to the VCO, and a mixer for combining incoming 1st intermediate frequency (IF) sigals within a 1st predetermined IF frequency range with the output of the VCO to reduce the frequency of the 1st IF signals to generate 2nd IF signals within a 2nd predetermined IF frequency range, and a filter for selectively rejecting undersired interference signals. The interference filter comprises separate trap means for respectively blocking out interfering signals having selected bottom and top trap frequencies, tuning means for adjusting the bottom and top trap frequencies, means for increasing the quality factor of the trap means, and means for selectively switching the trap means into and out of the receiver based on the presence or absence of signals which interfere with the received signals.

47838485, Nov 8, 1988

Oct 21, 1985

6/789424

John Y. Ma - Milpitas CA
David H. McCracken - San Jose CA

Capetronic (BSR) Ltd. - Kowloon

H04B 1116
H04B 126

455182

An improved satellite receiver system is provided which automatically locates audio signals among the various audio subcarriers received by an earth station; manual scanning of transmissions received from different transponders in order to locate audio signals embedded therein is eliminated. The improved receiver system does not require any input data characterizing the frequencies or bandwidth of the incoming audio signals and locates desired audio subcarriers in response to a command signal, without need for any manual intervention after generation of the command signal.

48019402, Jan 31, 1989

Oct 30, 1985

6/792786

John Y. Ma - Milpitas CA
David H. McCracken - San Jose CA
Steven Weiss - Los Gatos CA
Albert C. Houston - Santa Cruz CA

Capetronic (BSR) Ltd. - Kowloon

H01Q 300

342359

A TVRO earth station having a satellite seeking system comprising at least one controllable motor for adjusting the position of an antenna for receiving signals from a satellite having multiple transponders transmitting signals at prescribed nominal center frequencies and with different polarizations, control means for energizing the motor to move said antenna along a predetermined satellite-searching path, a receiver for receiving the incoming signals from the antenna and successively tuning to the center frequencies at each of a succession of intervals along the searching path, means responsive to the signals detected by the receiver for producing a signal or value representing the quality of the detected signals at each of the successive intervals along the searching path, and means responsive to the quality-representing signal or value for identifying the locations along the searching path at which the antenna receives signals from a satellite.

48167690, Mar 28, 1989

Jan 16, 1987

7/003843

John Y. Ma - Milpitas CA
Louis H. Jandrell - Cupertino CA

H03D 318
H03D 104

329 50

An FM receiver for the reception of digital data modulated on a Subsidiary Communication Authorization (SCA) subcarrier is provided with automatic tuning capability and a coherent demodulator for minimizing noise, distortion and interference. The FM receiver is tuned automatically to minimize the measured amplitude of noise and distortion at the high frequency end of the spectrum of the FM demodulator output, above the frequencies of the SCA signal. The SCA signal is tuned by a heterodyne circuit including a balanced modulator, a voltage-controlled oscillator (VCO), and a bandpass filter. The VCO is automatically tuned to maximize the measured amplitude of the SCA signal selected by the bandpass filter. For coherent detection of BPSK (Binary-Phase-Shift-Keying), the coherent demodulator is preferably and kind of data-aided Costas loop in which digital logic circuits perform phase shifting, phase detecting, a multiplying functions. The feedback of the phase error signal is preferably inhibited whenever the signal-to-noise ratio falls below the level which ensures phase-lock, for example, by inhibiting feedback whenever the amplitude of the filtered in-phase signal in the Costas loop fails to exceed a predetermined threshold level.

48767395, Oct 24, 1989

Dec 31, 1987

7/140037

John Y. Ma - Milpitas CA
Albert C. Houston - Santa Cruz CA

Capetronic (BSR) Ltd. - Kowloon

H04B 110

455266

A TVRO receiver for receiving frequency-modulated video signals, the receiver comprising a tuner including a superheterodyne circuit having a voltage-controlled oscillator (VCO), means for supplying a controlling input voltage to the VCO, and a mixer for combining incoming 1st IF signals with the output of the VCO to reduce the frequency of the 1st IF signals to a 2nd IF frequency which is sufficiently high to permit the output frequency of the VCO to be above the frequency range of the 1st IF signals, and a linear phase passband filter for passing a single video channel in the 2nd IF output from the mixer, the filter producing an output which is at least about 10 dB down from its peak at both +10 MHz and -10 MHz from the center of the passband of the filter.

50602977, Oct 22, 1991

Apr 4, 1988

7/176844

John Y. Ma - Milpitas CA
Bonnie Houston - Los Gatos CA

H04B 110

455302

A TVRO receiver for the reception of frequency modulated satellite broadcast signals is provided with the capability of efficiently rejecting image frequencies generated as the received signals undergo intermediate frequency translation. A TVRO tuner, which includes a super-heterodyne circuit having a voltage-controlled oscillator (VCO), means for supplying a controlling tuning voltage to the VCO, and a mixer for combining incoming 1st IF signals with the output frequency of the VCO to reduce the frequency of the 1st IF signals to a selected 2nd IF frequency, is provided with a tracking filter which is adapted to pass only the incoming 1st IF signals and effectively reject any image frequencies generated at the received signal frequencies. The tracking filter comprises at least one low-pass filter section and has a cut-off frequency which is controlled by the same tuning voltage used to regulate the output frequency of the VCO in such a way that the filter rejects frequencies exceeding the VCO output frequency. The filter is designed so that image frequencies, which are generated during the intermediate frequency translation stage as the sum of a given VCO output frequency and the selected 2nd IF frequency, fall substantially beyond the filter cut-off frequency and are thereby attenuated.

47929936, Dec 20, 1988

Oct 30, 1985

6/792783

John Y. Ma - Milpitas CA

Capetronic (BSR) Ltd. - Kowloon

H03J 116

455266

An improved TVRO receiver for receiving signals broadcast over a plurality of channels with varying bandwidths and having a tuner producing output signals corresponding to the received signals and having bandwidths which vary from channel to channel is provided with a band pass filtering arrangement receiving the output signals and having a controllably adjustable pass band, a bandwidth detection circuit for receiving the output signals passing through the filtering arrangement and being responsive to a current output signal corresponding to the channel being received for producing a control signal indicative of the extent of deviation of the bandwidth of the current output signal beyond the current pass band of the filtering arrangement, and a control circuit responsive to the control signal for adjusting the pass band of the filtering arrangement to accommodate the bandwidth of the current output signal corresponding to the channel being received, if the bandwidth deviation of the current output signal exceeds a predetermined threshold value.

46268626, Dec 2, 1986

Aug 8, 1984

6/639667

John Ma - Milpitas CA

H01Q 124

343702

An elongated active element for an antenna has an internal resonator providing a high quality matching impedance. The internal resonator is formed by a pair of conductors including an outer conductor and a coaxial inner conductor that is connected to signal ground. The signal connection of the active element is made to one end of the outer conductor in the neighborhood of the ground connection to the inner conductor. The inner conductor is shorted to the outer conductor at approximately a quarter of a wavelength, plus an integral number of half wavelengths, from the signal and ground connections to provide a parallel-resonant condition complementing the series resonant characteristics of the radiation impedance of the active element. Preferably, the active element is approximately a quarter wavelength long, and may be lengthened or shortened to obtain a desired radiation resistance. The antenna is easily fabricated from a length of coaxial cable.